anagram

elixir/anagram/lib/anagram.ex

@@ -0,0 +1,21 @@
+defmodule Anagram do
+  @doc """
+  Returns all candidates that are anagrams of, but not equal to, 'base'.
+  """
+  @spec match(String.t(), [String.t()]) :: [String.t()]
+  def match(base, candidates) do
+    candidates
+    |> Enum.filter(&anagram?(normalize(base), normalize(&1)))
+  end
+
+  defp anagram?(base, base), do: false
+  defp anagram?(base, candidate), do: hash(base) == hash(candidate)
+
+  @spec normalize(String.t()) :: String.t()
+  defp normalize(string), do: string |> String.downcase() |> String.graphemes()
+
+  @spec hash(String.t()) :: Map.t()
+  defp hash(string) do
+    Enum.reduce(string, %{}, fn char, acc -> Map.update(acc, char, 1, &(&1 + 1)) end)
+  end
+end